This invention relates in general to new and useful improvements in blow molded bottles formed of a plastics material such as polyethylene terephthalate, or PET.
Most specifically, this invention relates to the formation of a bottle formed of a plastics material which is suitable for containing liquids under pressure such as carbonated beverages.
The bottling of carbonated beverages in plastics material bottles presents a number of problems, many of which arise in connection with the base or bottom structure of the bottle. The mere duplication in plastic of traditional glass bottle bottom configurations is unsatisfactory because of the tendency of plastic materials to creep or become distorted under pressure, especially in the presence of elevated temperatures which may be encountered curing, shipment and storage. Such distortions may alter the shape and dimensions of the traditional bottom configuration to the extent that the liquid level within the bottle falls below the normal fill line, thereby raising a question by a customer as to whether he is receiving full quantity. In addition, the bottom or base of the bottle may become distorted so as to become unstable when seated on a flat surface.
This invention most particularly related to a plastic material bottle intended to contain carbonated beverages under pressure wherein the bottom configuration is that of the so-called champagne bottle. While relatively successful champagne bottom plastic material bottles have been produced which are acceptable to the public, such bottoms still have a tendency to creep, particularly when the available material is held to a minimum. It is therefore proposed in accordance with this invention to reinforce or stiffen the bottom structure by using a minimum of additional plastic material, the stiffening being in the form of radiating ribs which are in the form of added solid material disposed internally of the bottle.
It has been found that the required rib arrangement can be formed on the bottle bottom by the simple formation of ribs on the lower portion of the preform from which the bottle is blow molded.
Further, it has been found that the necessary ribs can be readily formed on the preform by machining grooves in existing mold core members. Therefore, in accordance with this invention, it has been found that the necessary preform can be readily formed with a minor change in existing equipment and that, further, the desired rib reinforced bottom bottle can be formed utilizing the same equipment as heretofore utilized in the forming of an identical bottle but without the stiffening ribs.
The axial extent of the ribs may be varied and, when a minimum of reinforcement is desired, the ribs may be substantially entirely on the hemispherical bottom part of the preform and located so that when the preform is blown into a bottle the ribs will be primarily at the reverse turn between the generally cylindrical outer part of the bottom and the upwardly and inwardly directed bottom portion.
On the other hand, the ribs may be quite pronounced on the preform and extend further radially inwardly adjacent the extreme bottom of the preform so that in the blown bottle the ribs are rather pronounced and extend almost to the center of the bottom. In such event, the ribs may have a beneficial effect on the filling of the bottle in that they will control the swirling of the liquid as it is directed against the bottom portion of the resultant bottle.
Much effort has been devoted in the past to the reinforcement or stiffening of a champagne bottom bottle. Typical examples of the prior art efforts are found in the patent to Chang U.S. Pat. No. 4,134,510 and Krishnakumar et al U.S. Pat. No. 4,108,324, both of which patents relate to the reinforcement or stiffening of a champagne bottom bottle by the provision of ribs which require relatively complex molds and wherein all of the rib formations are disposed externally of the bottle and therefore do not present a smooth outer surface on the bottom of the bottle as is desired to provide a stable base.
With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims, and the several views illustrated in the accompanying drawings.